There are a couple of possible reasons for the leaves of ming aralia (Polyscias fruticosa) to turn yellow and drop. A sudden temperature fall causes this tropical plant's leaves to lose their color and fall off. However, if the temperature change is gradual enough, aralias can acclimate to 65°F just fine. Drafts can cause a similar reaction. If there are no signs of pest infestation such as scale on the stems or leaves, leaf drop is probably due to changes in temperature. 

Another issue that could cause yellowing of leaves is over-watering. Most large specimens of ming aralia have virtually no roots in the top 2-3 inches of soil. For these large plants, when the soil has dried down 2 or 3 inches from the surface, water sparingly with tepid water all the way around the plant. Water early in the day, not at night. The trick is to water only enough to get some water to the bottom of the pot where the roots are, with a little water seeping from the drain holes, keeping very little in the saucer. If too much water fills the saucer, drain out the excess to avoid root rot.

For tips on a variety of gardening topics, see Plant Information Service guides - https://libguides.nybg.org/portalpage.

- Courtesy of NYBG Plant Information Service